5.2 and CO2 Off Flavor

I've brewed 21 all grain batches with great results and have never worried about my mash pH until recently. I added 1 tablespoon of Five Star's 5.2 mash stabilizer to each of my last two beers, an ESB and American Amber. Before kegging, both beers tasted young but right where they should be. Once kegged, I hooked both up to CO2 at 12 psi for a week. Upon tasting both after a week, I noticed that they developed an awful metallic mineral like taste that was not there at kegging. Since I brew 6 gallon batches, I always have some leftover in the fermenter once the keg is full, so I fill up a couple of bombers just to have around. I also tried the bombers of uncarbonated beer, and none of them have developed the terrible flavor that the kegs did.

My sanitation practices are sound, and have never had the slightest infection. I have full fermentation temperature control, so that is not a factor either.

The only thing that makes any sense to me is that adding CO2 (carbonic acid with a pH around 4 at a pressure of 12 psi) to the beer is activating the buffer in 5.2 and producing this flavor.

If anyone has had this experience or can lend any insight, it would be greatly appreciated.

Two questions: 1) If you hadn't had any problems why did you decide to add this product to your beer? 2) Do you know what your water analysis profile is?

The 5.2 stuff is metallic phosphate salts, probably either sodium or potassium. (The manufacturer doesn't say what is in it exactly) Potentially, the ions in the 5.2 combined with metallic ions already in your brewing water resulted in enough of something to create a noticeable off flavor accented by the CO2.

1) I'm an idiot and like messing with things, even when they're fine. I figured the buffer would be harmless since no huge pH swings would be seen.

2) Unfortunately, I do not know my water profile.

Maybe this will just be a tough lesson in not tinkering.

mlaw06 said:

1) I'm an idiot and like messing with things, even when they're fine.

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mlaw06 said:

2) Unfortunately, I do not know my water profile.

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Do yourself and your beer a favor and find out. This is something that you should have if brewing all grain.

I've been using pH5.2 for years and keg. I've have never noticed any metallic flavors. Since I often take beer to club meetings, I'm certain someone would have mentioned it. The pH of naturally carbonated and force carbonated beer doesn't vary much.

It is certainly possible that something in your water is reacting with the pH5.2, so getting the profile would be a good idea.

You're probably picking up some of the initial carbonic acid that is created as CO2 dissolves. It's worse in the first week or so of kegging when most of the co2 is dissolved. The acid will dissipate after some time which is why I never drink beer that I've recently put on the gas..

Bobby_M said:

You're probably picking up some of the initial carbonic acid that is created as CO2 dissolves. It's worse in the first week or so of kegging when most of the co2 is dissolved. The acid will dissipate after some time which is why I never drink beer that I've recently put on the gas..

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huh....that's interesting and useful information. can't believe i've never heard of this before.

I should disclose that I'm not a chemist so I could be completely wrong on this one. I just know that I get the same metallic taste when I first put the gas on.

Yea I'm going to let both mature for a few weeks and see how they are then. I did get feedback from someone who got that metallic taste when there was some residual PBW left in the keg after cleaning. I wash my kegs with PBW and thought I rinsed thoroughly, but maybe I'm not rinsing enough.

Bobby_M said:

I should disclose that I'm not a chemist so I could be completely wrong on this one. I just know that I get the same metallic taste when I first put the gas on.

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Bobby is spot on with this one. I've noticed that taste too. It definitely goes away after a week or so.

Good point guys. I don't force-carbonate without giving the beer time to condition, so I probably haven't noticed the problem.

Did you purge your keg prior?